Layering conversion method of composite material beam

Abstract

The invention discloses a paving layer conversion method of a composite material beam. The method comprises the following steps: S1, paving material sheets of a first paving layer group (1) on a lower die (5), and vacuumizing and compacting at normal temperature; s2, the material sheets of the second laying layer group (2) are sequentially laid on the first laying layer group (1) which is subjected to normal-temperature vacuum pumping and compaction, and normal-temperature vacuum pumping and compaction are carried out; during laying, the material sheets of the second laying layer group (2) and the edge strip areas between the first layer of material sheets of the second laying layer group (2) and the first laying layer group (1) are isolated by isolating membranes or backs of the material sheets; s3, after the second laying layer group (2) is laid and compacted, the upper mold (6) and the lower mold (5) are closed; s4, after the mold is closed, separating films or back liners of edge strip areas of all the material pieces of the second laying layer set (2) are pulled away, then the edge strip areas are sequentially wrapped back to the upper mold (6), and normal-temperature vacuumizing compaction is carried out; s5, the corners of the first laying layer set and the second laying layer set are filled with rhodomyrtus tomentosa strips (9); after filling is finished, the third laying layer set (3) and the fourth laying layer set (4) on the side mold body A (7) and the side mold body B (8) continue to be laid, and normal-temperature vacuumizing compaction is conducted; then the two side molds are closed; and S6, after the two side molds are assembled, vacuum curing is carried out. According to the invention, wrinkles of the cloth layer between the first layer group and the second layer group in the L-shaped flanging area of the web can be effectively controlled.

Description

Technical Field

[0001] The invention belongs to the technical field of composite material forming, and in particular relates to a ply conversion method for a composite material beam. Background Art

[0002] With the rapid application of composite materials in modern aviation, the main load-bearing beam of the helicopter vertical tail has also begun to use all-composite parts.

[0003] The vertical tail beam is a high-temperature carbon fiber solid part with a T-shaped cross section. The T-shaped edge strip is connected to the vertical tail skin. There is a square opening at the root of the vertical tail beam, and the opening is an L-shaped edge strip. The cable bracket is riveted on the edge strip. The L-shaped edge strip also serves to increase the strength of the part. Figure 1 , its structure includes T-shaped edge strip Ⅰ at the edge of the I-beam and L-shaped edge strip Ⅱ at the root of the square opening.

[0004] The vertical tail beam ply is divided into 4 groups, according to the traditional typical I-beam ply method (see Figure 2 ), lay the first ply group on the lower mold body; lay the second ply group on the upper mold body; then close the upper and lower mold bodies. Lay the third and fourth ply groups on the two side mold bodies respectively, and then close the two side molds.

[0005] There is a certain compression-to-thickness ratio before and after the prepreg is cured, which is generally between 1.2 and 1.5. That is, at room temperature, the thickness of the layer is higher than the thickness of the layer after curing. As the curing process of the part proceeds, under the action of pressure and temperature, as the interlayer gap decreases and the interlayer resin overflows, the cavity gap between the upper mold, the lower mold, and the side mold gradually becomes smaller, and the layer gradually becomes thinner until it reaches a stable state to form the thickness of the part after curing. Therefore, the traditional layering process can complete the typical I-beam (I-beam without flange on the web) part layering. However, when the web has an L-shaped flange, during the closing process of the upper and lower molds, the sum of the thickness of the first layer group and the second layer group at the position of the L-shaped flange of the web of the I-beam is much higher than the cavity gap between the upper and lower molds, resulting in interference of the layers and the inability of the molding tool to close the mold in place; at the same time, the layers between the first layer group and the second layer group in the L-shaped flange area of ​​the web of the I-beam will have severe wrinkles (see Figure 3 ). Summary of the invention

[0006] The purpose of the present invention is to provide a ply conversion method for a composite beam, which can effectively control wrinkles in the fabric layer between the first ply group and the second ply group in the L-shaped flange area of ​​the web.

[0007] The technical solution of the present invention is: a ply conversion method for a composite beam, comprising the following steps:

[0008] S1. Lay the sheet of the first ply group on the lower mold and perform vacuum compaction at room temperature;

[0009] S2. The sheets of the second ply group are sequentially laid on the first ply group that has been vacuum compacted at room temperature, and vacuum compacted at room temperature; when laying, the edge strip areas between the sheets of the second ply group and between the first sheet of the second ply group and the first ply group are isolated with an isolation film or a backing provided by the sheet;

[0010] S3. After the second layer group is laid and compacted, the upper mold and the lower mold are closed;

[0011] S4. After the mold is closed, the edge strip area of ​​each sheet of the second layer group is torn off the isolation film or backing, and then it is sequentially wrapped back onto the upper mold, and vacuumed and compacted at room temperature;

[0012] S5. Fill the corners of the 1st and 2nd ply groups with twist strips; after the filling is completed, continue to lay the 3rd and 4th ply groups on the side mold body A and the side mold body B, and perform vacuum compaction at room temperature; then close the two side molds;

[0013] S6. After the two side molds are closed, vacuum curing is performed.

[0014] In the aforementioned ply conversion method of the composite beam, the room temperature vacuum compaction method is as follows: after laying the first layer of material sheets, the first layer of material sheets is kept at room temperature for 30 to 40 minutes in an environment with a negative pressure of not less than 0.07 MPa for compaction; thereafter, compaction is performed once every 3 to 4 layers of material sheets are laid using the same method.

[0015] In the above-mentioned ply conversion method of the composite beam, in step S1, after the first ply group is laid, hot compaction is performed, and the hot compaction parameters are: after heating to 60°C, keep warm for 30 minutes, negative pressure is not less than 0.07MPa, positive pressure is 0.6±0.02MPa, heating and cooling rate is 0.5~2°C / min, and pressure increase rate is 0.02~0.025MPa / min;

[0016] In the aforementioned ply conversion method for composite beams, in step S3, after the mold is closed, compaction is performed under a negative pressure of not less than 0.09 MPa at room temperature.

[0017] In the aforementioned ply conversion method for composite beams, the mold clearance between the upper mold and the uppermost sheet after compaction is less than 0.5 mm.

[0018] In the aforementioned layup conversion method for composite beams, in step S5, the mold clearance of the side mold bodies is ≤0.2 mm.

[0019] In the aforementioned ply conversion method for composite beams, the vacuum degree of vacuum curing in step S6 is detected as follows: the vacuum degree of the vacuum bag reaches 0.09 MPa until the vacuum degree is stable, the vacuum source is disconnected or turned off after 15 minutes, and the vacuum gauge reading drops by no more than 0.017 MPa within 5 minutes.

[0020] In the aforementioned ply conversion method for composite beams, when the sheets of each ply group are laid, the sheets are straightened and tightened to drive out all bubbles.

[0021] The advantages of the present invention are:

[0022] The present invention can avoid wrinkles caused by relative movement between the fabric layers of the first ply group and the second ply group in the L-shaped flanging area of ​​the web during the mold closing process, and can ensure that the mold is closed in place.

[0023] The present invention adopts the method of converting the plies of the first ply group of the upper mold to be laid on the lower mold, and at the same time increasing hot compaction during the ply laying process to reduce the compression ratio of the prepreg; the relative movement between the cloth layers in the original mold closing process is converted into the relative movement between the cloth layers and the tooling, Figure 4 The method has the following advantages:

[0024] 1) Ensure accurate mold closing of the L-shaped flange area of ​​the web;

[0025] 2) Eliminate wrinkles;

[0026] 3) Reduce the difficulty of closing the upper and lower molds;

[0027] 4) Improve internal product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the vertical tail front beam;

[0029] Figure 2 It is a simplified schematic diagram of the traditional I-beam laying process;

[0030] Figure 3 It is a simplified schematic diagram of an I-beam with an L-shaped flange on the web laid according to the traditional I-beam laying process;

[0031] Figure 4 It is a schematic diagram of the operation flow of the present invention. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0033] The features and illustrative embodiments of various aspects of the present invention will be described in detail below. In the detailed description below, many specific details are proposed to provide a comprehensive understanding of the present invention. However, it is obvious to those skilled in the art that the present invention can be implemented without the need for some of these specific details. The following description of the embodiments is only to provide a better understanding of the present invention by illustrating examples of the present invention. The present invention is by no means limited to any specific settings and methods proposed below, but covers any improvements, replacements and modifications of structures, methods, devices without departing from the spirit of the present invention. In the accompanying drawings and the following description, known structures and technologies are not shown to avoid unnecessary ambiguity in the present invention.

[0034] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other, and the embodiments can refer to and quote each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0035] Example 1. A ply conversion method for a composite beam, see Figure 4 , including the following steps: Step 1: Tooling preparation

[0036] (1) Tool collection: collect tooling according to the tooling drawing number and check the tooling certificate;

[0037] (2) Tool inspection: Visually inspect the tool, including whether the tool surface is worn or rusted, and whether the tool surface is dented, scratched or rusted.

[0038] Step 2: Material preparation

[0039] (1) Collecting the materials;

[0040] (2) Low-temperature materials should be thawed in an air-conditioned room. During the thawing period, the materials should be kept sealed. Before opening the sealed bag, ensure that no moisture is formed inside or outside the bag;

[0041] (3) The matched materials are not allowed to be folded and can be stored flat or rolled up with support.

[0042] Step 3: Cutting

[0043] (1) Use the correct CNC prepreg cutting according to the material page and corresponding procedures. The cut pieces should be marked with the following: product drawing number, ply number, angle, and fiber direction of the cloth;

[0044] (2) Lay the sheets flat in order according to the order of the sheets, and check the integrity of the sheets and the clarity and completeness of the markings.

[0045] Step 4: Lay Up

[0046] (1) Lay the first layer of the sheet in the first layup group 1 on the lower mold according to the projection program. When laying the sheets, straighten and tighten them to drive out all bubbles;

[0047] (2) Vacuum compaction at room temperature. Use a non-porous isolation film during the vacuum process. Start timing after the vacuum bag reaches the pressure value. The negative pressure is not less than 0.07 MPa and the time is 30 to 40 minutes.

[0048] (3) After laying the first layer, lay the remaining sheets according to the projection procedure. After laying 3 to 4 layers of sheets, vacuum compaction is performed once, in the same manner as in step 2, until the last layer of sheets in the first laying group 1 is laid;

[0049] (4) After all the sheets in the first layer group 1 are laid on the lower mold 5, hot compaction is performed. The hot compaction parameters are: after heating to 60°C, keep warm for 30 minutes, negative pressure is not less than 0.07MPa, positive pressure is 0.6±0.02MPa, heating and cooling rate is 0.5~2°C / min, and pressure increase rate is 0.02~0.025MPa / min;

[0050] (5) After the lower mold 5 is hot-compacted and cooled to room temperature, the sheets in the second layup group 2 originally laid on the upper mold 6 are transferred and laid on the lower mold 5. First, the outermost sheet in the second layup group 2 is laid on the lower mold 5 according to the projection procedure. At this time, the outermost sheet in the second layup group 2 and the last sheet in the first layup group 1 are only placed against the web area, and the edge strip area is isolated with an isolation film or the sheet's own backing;

[0051] (6) After laying the outermost sheet in the second ply group 2, vacuum compaction is performed at room temperature in the same manner as in step 2;

[0052] (7) After the outermost sheet in the second layer group 2 is laid, the remaining sheets in the second layer group 2 are laid in sequence according to the projection procedure, wherein all sheets are isolated in the edge strip area with an isolation film or a backing provided by the sheet;

[0053] (8) The remaining layers of the sheets in the second layer group 2 are compacted once after every 3 to 4 layers are laid, in the same manner as in step 2. During this process, support and protection are provided in the transition area isolated by the sheets to prevent wrinkles that cannot be eliminated after curing from forming in the sheets isolated by the isolation film or backing during vacuum compaction.

[0054] (9) After all the sheets in the second layup group 2 are laid on the lower mold 5, the mold is closed. At this time, there is no sheet on the upper mold 6, and all the sheets in the first layup group 1 and the second layup group 2 have been laid on the lower mold 5.

[0055] (10) Paste the vacuum bag, vacuum and compact it at room temperature, start timing after the vacuum bag reaches the pressure value, the negative pressure is not less than 0.09MPa, and end when the mold gap between the upper mold 6 and the prepreg is less than 0.5mm;

[0056] (11) After removing the vacuum bag, all the fabric layers of the edge strip in the second layer group 2 separated by the isolation film are packed back onto the upper mold 6. During the packing process, the sheet is straightened and tightened to drive out all bubbles;

[0057] (12) After the repacking process is completed, vacuum compaction is performed in the same manner as in step 2;

[0058] (13) Fill the corner where the upper and lower molds meet with twist strips 9. After filling, continue to lay all the fabric layers of the third layer group 3 and the fourth layer group 4 of the side mold body A7 and the side mold body B8 according to the projection program. Compact once after laying 3 to 4 layers. The method is the same as step 2.

[0059] (14) After all the sheets in the third layup group 3 and the fourth layup group 4 are laid, the side mold 1 and the side mold 2 are closed respectively to ensure that the mold clearance between the side mold 1 and the side mold 2 is less than or equal to 0.2 mm;

[0060] Step 5: Paste the final vacuum bag;

[0061] ① Check the quality of the vacuum bag paste and the correct placement and quantity of the vacuum nozzles;

[0062] ② Vacuum degree detection: The vacuum degree of the vacuum bag reaches 0.09MPa until the vacuum degree stabilizes. After 15 minutes, the vacuum source is disconnected or turned off. The vacuum gauge reading should not drop by more than 0.017MPa within 5 minutes.

[0063] Step 6: Curing

[0064] Curing is performed according to corresponding curing parameters;

[0065] Step 7: Start the mold

[0066] Insert the demoulding wedge evenly into the gap between the edge of the part and the tooling. After ensuring that the edge of the part is free from the tooling, insert the demoulding wedge evenly around the part. Do not use excessive force during the operation.

[0067] Step 8: Marking

[0068] Mark product drawing number, edition, serial number and other information on the product;

[0069] Step 9: Cutting

[0070] Cut off the part outside the margin line according to the edge line of the product.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the field can easily think of various equivalent modifications or substitutions within the technical scope disclosed by the present invention, and these modifications or substitutions should all be covered within the protection scope of the present invention.

Claims

1. A ply conversion method for a composite beam, characterized in that: The steps include: S1. The sheet of the first ply group (1) is laid on the lower mold (5) and compacted by vacuum evacuation at room temperature; S2. The sheets of the second ply group (2) are sequentially laid on the first ply group (1) which has been subjected to vacuum compaction at room temperature, and vacuum compaction is performed at room temperature; when laying, the edge strip areas between the sheets of the second ply group (2) and between the first layer of sheets of the second ply group (2) and the first ply group (1) are isolated with an isolation film or a backing provided by the sheets; S3. After the second layer group (2) is laid and compacted, the upper mold (6) and the lower mold (5) are closed; S4. After the mold is closed, the edge strip area of ​​each sheet of the second layer group (2) is torn off the isolation film or backing and then sequentially backpacked to the upper mold (6), and vacuum compacted at room temperature; S5. Fill the corners of the first and second ply groups with twist strips (9); after filling, continue to lay the third ply group (3) and the fourth ply group (4) (4) on the side mold body A (7) and the side mold body B (8), and perform vacuum compaction at room temperature; then close the two side molds; S6. After the two side molds are closed, vacuum curing is performed.

2. The ply conversion method of a composite beam according to claim 1, characterized in that: The room temperature vacuum compaction method is as follows: after laying the first layer of sheets, keep the first layer of sheets at room temperature for 30 to 40 minutes in an environment with a negative pressure of not less than 0.07 MPa for compaction; thereafter, compact once every 3 to 4 layers of sheets are laid using the same method.

3. The ply conversion method of a composite beam according to claim 1, characterized in that: In step S1, after the first ply group (1) is laid, hot compaction is performed, and the hot compaction parameters are: after heating to 60°C, keep warm for 30 minutes, negative pressure not less than 0.07MPa, positive pressure 0.6±0.02MPa, heating and cooling rate 0.5~2°C / min, pressure increase rate 0.02~0.025MPa / min.

4. The ply conversion method of a composite beam according to claim 1, characterized in that: In step S3, after the mold is closed, compaction is performed under a negative pressure of not less than 0.09 MPa at room temperature.

5. The ply conversion method of a composite beam according to claim 4, characterized in that: After compaction, the mold clearance between the upper mold and the uppermost sheet is less than 0.5mm.

6. The ply conversion method of a composite beam according to claim 1, characterized in that: In step S5, the mold clearance of the side mold body is ≤0.2mm.

7. The ply conversion method of a composite beam according to claim 1, characterized in that: The vacuum degree of vacuum curing in step S6 is detected as follows: the vacuum degree of the vacuum bag reaches 0.09 MPa until the vacuum degree is stable, the vacuum source is disconnected or turned off after 15 minutes, and the vacuum gauge reading drops by no more than 0.017 MPa within 5 minutes.

8. The ply conversion method of a composite beam according to claim 1, characterized in that: When laying the sheets of each ply group, straighten the sheets, tighten them, and drive out all bubbles.

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